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Python program to sort a list of tuples in increasing order by the last element in each tuple

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mahmoud2506
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2022-05-23
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Example:

tuple = ("python", "includehelp", 43, 54.23)

List is a sequence data type. It is mutable as its values in the list can be modified. It is a collection of ordered set of values enclosed in square brackets [].

Example:

list = [3 ,1,  5, 7]

A list of tuples is a list whose each element is a tuple.

Example:

upList = [("python", 7), ("learn" , 1), ("programming", 7), ("code" , 3)]

Sorting a list of tuples in increasing order by the last element in each tuple

We need to sort the List of Tuples in Increasing Order By the last Element in Each Tuple. For this, we will be simply sorting the List but the value to be used while comparison will be the second value of the list.

We can write our sorting code or we can use built-in python methods to perform the task.

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All Answers

mahmoud2506
2022-05-23
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Method 1: Writing sorting code

We can use any sorting technique and use the sorting value to be the second element of the tuple. Here, we will use bubble sort with tup[2] as the comparison value.

Program:

# Python program to sort a list of tuples in 
# increasing order by the last element in each tuple

# Creating and Print list 
tupList =[(5, 7), (12, 4), (20, 13), (45, 2)]
print("List of Tuple before sorting : " + str(tupList))

# Sorting List of Tuples in Increasing order by last element 
listLen = len(tupList); 
for i in range(0, listLen):
    for j in range(0, listLen - i - 1):
        if(tupList[j][-1] > tupList[j + 1][-1]):
            swap = tupList[j]
            tupList[j] = tupList[j + 1]
            tupList[j + 1] = swap

#Printing Sorted List 
print("List of Tuple after sorting : " + str(tupList))

Output:

List of Tuple before sorting : [(5, 7), (12, 4), (20, 13), (45, 2)]
List of Tuple after sorting : [(45, 2), (12, 4), (5, 7), (20, 13)]

Method 2:

We can also perform the task of sorting by the last element using built-in methods provided in the python library.

There are two such methods to perform the task. They are,

(i) Sorted() method

The sorted method in the python library is used to return a sorted list. We will pass parameters to use the last value of tuple to sort the list based on the last value of the tuple.

Program:

# Python program to sort a list of tuples in 
# increasing order by the last element in each tuple

def last(n):
    return n[-1]  

# Creating and Print list 
tupList =[(5, 7), (12, 4), (20, 13), (45, 2)]
print("List of Tuple before sorting : " + str(tupList))

# Sorting List of Tuples in Increasing order by last element 
sortedTupList = sorted(tupList, key=last)

#Printing Sorted List 
print("List of Tuple after sorting : " + str(sortedTupList))

Output:

List of Tuple before sorting : [(5, 7), (12, 4), (20, 13), (45, 2)]
List of Tuple after sorting : [(45, 2), (12, 4), (5, 7), (20, 13)]

(ii) sort() method

The sort() method also sorts the given list and takes a lambda function for defining the key and order of sorting.

Program:

# Python program to sort a list of tuples in 
# increasing order by the last element in each tuple

# Creating and Print list 
tupList =[(5, 7), (12, 4), (20, 13), (45, 2)]
print("List of Tuple before sorting : " + str(tupList))

# Sorting List of Tuples in Increasing order by last element 
tupList.sort(key = lambda x: x[-1])

#Printing Sorted List 
print("List of Tuple after sorting : " + str(tupList))

Output:

List of Tuple before sorting : [(5, 7), (12, 4), (20, 13), (45, 2)]
List of Tuple after sorting : [(45, 2), (12, 4), (5, 7), (20, 13)]

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